Bicycles are extremely popular for both transportation and particularly for recreation and exercise. High performance off-road bicycles, also called mountain bikes, are widely used for traversing rugged terrain. Like a touring bicycle, a mountain bicycle desirably has a relatively low weight to reduce rider fatigue. Accordingly, the frame and components of a bicycle are desirably light in weight, yet sufficiently strong to reduce the likelihood of damage to the bicycle. The frame and other components of a mountain bike, in particular, may be subjected to very high loads caused by intentional, as well as unintentional jumps, falls, or drops.
A typical bicycle includes a tubular frame having a tubular member to receive a seat post assembly. A seat post assembly, in turn, typically includes a tube adapted to be inserted into the frame member, and a clamp arrangement on the upper end of the tube. The clamp grips a pair of longitudinal seat rails that are, in turn, connected to and extend from an underside of the bicycle seat. The height of the seat relative to the bicycle frame is readily adjustable between minimum and maximum positions for the rider's comfort. The seat angle and its longitudinal position may also typically be adjusted.
U.S. Pat. No. 4,783,119 to Moses discloses a seat post including a seat tube having a concave recess at its upper end. A lower clamp member fits within the concave recess and cooperates with a pair of upper clamp members to secure a pair of seat rails. In addition, a longitudinal rod or pair of integrally formed ears adjacent the upper end of the tube may be symmetrically positioned and include openings to receive a pair of respective bolts to thereby secure the clamp members together and permit adjustment of seat angle.
U.S. Pat. No. 5,190,346 to Ringle discloses a bicycle seat post and clamp including a separate wrap around clamp strap for securing upper and lower clamp members together. The upper end of the seat tube includes a laterally extending recess to receive the lower clamp member. A pin extends longitudinally through the seat tube beneath the recess. The wrap around clamp strap attaches directly to one end of the pin, while a bolt secures the other end of the strap to the other end of the pin.
Unfortunately, a seat post and clamp assembly may experience relatively high loads when a substantial part or all of the rider's weight is brought down onto the seat. The seat post and associated clamp of a mountain bike, in particular, are likely to experience even higher loads as the rider executes jumps and other stunts, where forces greater than the rider's full weight may be imparted to the seat. A conventional seat post and clamp may experience a catastrophic failure during such high loads. Catastrophic failure means that the clamp or end of the seat tube fails, thus allowing the seat to fall away from the bicycle. In other words, since the seat tube may typically be stronger than the clamp, the clamp, the fasteners, or the head of the tube may break allowing the seat to separate and exposing an upper end of the seat tube, for example. Accordingly, such a catastrophic failure increases the risk of injury to the rider.
Conventional seat posts and clamps may not be adjustable over a relatively large range of angles, and with the various components being relatively strong even at the extreme angular positions. Since the spacing between the seat rails and the underside of the seat may be limited, a low profile clamp may be preferred. Moreover, upper portions of a clamp, such as a bolt, for example, which extend upward beyond the upper clamp member may pose a risk of puncturing the seat and injuring a rider. Yet another difficulty with conventional seat posts and clamps is that the angular adjustment of the seat may be difficult to, set or reset to a desired angle.